1. The Field of the Invention
The present invention relates to iontophoretic drug delivery devices, and methods of manufacturing the same.
2. The Relevant Technology
There is an ongoing search for methods of medication delivery which are less invasive, less painful, and more efficient than conventional methods. For example, hypodermic injection of medication commonly entails pain and risk of infection. Oral ingestion of medication entails absorption of the drug from the digestive tract into the blood stream, wherein the blood containing the drug first percolates through the liver before entering the general circulation for delivery to the target tissue. In turn, much of an orally ingested drug may be metabolically inactivated before it has a chance to exert its pharmacologic effect. Local delivery of drugs therefore presents advantages over oral administration, an application characterized by inefficiency and unpredictability, and over hypodermic injection, an invasive, inconvenient, and sometimes risky technique.
One such local delivery method is known as iontophoresis. Iontophoresis is a safe, effective, non-invasive, and relatively painless medication delivery system. Iontophoresis involves the interaction between ionized molecules of a drug and an external electric field, resulting in the migration of charged molecules. The migration is achieved by placing two electrodes on the patient's skin, and connected to a DC power supply. One of the electrodes is an "active" electrode filled with a drug solution. The other electrode is an "inactive" electrode filled with an electrolyte solution. The electric field generated between the two electrodes causes the charged drug molecules to migrate from the active electrode into the tissues and blood stream of the patient.
Iontophoretic devices conventionally include a circuit board, electrodes and drug reservoirs which are fabricated separately, and then incorporated, together with electrical connections, in a housing. Rigid elements have conventionally been preferred over flexible elements because it was believed that it was easier to manipulate and maneuver rigid elements relative to one another in restricted spaces. Further, it was believed that rigid elements would not bend or deform during the assembly process, making the task more suitable for automation. However, rigid elements have proved less than ideal for suitable conformance to the body of a patient.
The device of U.S. Pat. No. 5,314,502 (hereinafter, "the '502 patent) is directed to a device which is flexible enough to conform to the contours of a patient's body. The '502 patent discloses an iontophoretic delivery device comprising a flexible housing having a flexible printed circuit board mounted therein, and a battery connected to the flexible printed circuit board. The flexible printed circuit board is connected to a pair of electrodes which each sit on top of a reservoir Each reservoir is in contact with the skin during in use.
However, certain problems are associated with the device of the '502 patent. The flexible printed circuit board carries a number of integrated circuit elements on its upper surfaces within a cavity in the flexible housing. The flexibility necessary to ensure conformity with the contours of the body means that the integrated circuits can be damaged by pressure exerted on the housing or by a shock occurring which could cause the integrated circuits to be crushed within the housing.
Furthermore, the battery, electrodes and connecting wiring are embedded within the housing making manufacture of the device difficult to achieve, which increases the expense of the device.